Lamp

ABSTRACT

The invention relates to a lamp that radiates visible light and infrared light. According to the invention, the lamp bulb ( 4 ) of the lamp comprises at least a first region ( 6 ) which is at least partly permeable to infrared light and at least partly impermeable to visible light, and at least a second region ( 9 ) which is wholly or partly permeable at least to visible light.

The invention relates to a lamp which radiates visible light andinfrared light.

Such a lamp is known as a light source from DE 100 27 018 A1 and is usedin a headlight. The vehicle headlight comprises a reflector, a lens, anda screen and operates by the projection principle. Light emitted by thelamp is reflected by the reflector. The screen and the lens are arrangedin the radiation path of a reflected light beam. In the “low-beam”operational position, the light beam in the visible wavelength rangeissuing from the headlight is a low beam illuminating a close range. Thescreen is at least partly permeable to light in the infrared wavelengthrange at least locally. The light passing through the screen in theinfrared wavelength range is a high beam and irradiates a long-distancerange. The long-distance range is registered by a sensor device andpresented to the vehicle's driver by means of a display device.

The invention has for its object to provide a simple lamp forilluminating the close range with light in the visible wavelength rangeand at the same time irradiating a long-distance range with infraredlight.

This object is achieved by the characteristics of claim 1. According tothe invention, a lamp bulb comprises at least a first region which is atleast partly permeable to infrared light and which is at least partlyimpermeable to visible light, and at least a second region which iswholly or partly permeable at least to visible light. These two regionsof the lamp bulb primarily serve to provide the desired lightdistribution for the lighting installation. Substantially the entirelight emission of the lamp is realized through these regions of the lampbulb. Further regions of the lamp bulb, which do not serve this purposeor in a secondary sense only, are, for example, the region of the pinch.In addition to visible light, the lamp also realizes a defined emissionof infrared light, while only integral components of the lamp bulb takepart in the filtering of the light issuing from the lamp bulb. As aresult the lamp is capable of performing two lighting functions, i.e.for example infrared light for long distance and visible light for shortdistance. When the lamp or a lighting installation comprising such alamp is used for this purpose in conjunction with a night visionapparatus or as a component of such an apparatus, which uses at leastinfrared light functionally, an improvement and enhancement of the fieldof vision of the user is achieved, while dazzling of persons in theilluminated region is avoided to a very high degree. No essentialconstructional changes of the lamp bulb are necessary in spite of theadded function, i.e. of a filtering function of at least a region of thelamp bulb. A night vision apparatus for a motor vehicle using at leastinfrared light as part of its function, denoted IR night visionapparatus for short, comprises at least a light source from which atleast infrared light enters the desired region, in particularly a regionin front of the vehicle and beyond the low-beam region illuminated byvisible light. A night vision apparatus in addition comprises aninfrared detector or a sensor device which detects the region in frontof the vehicle irradiated by the infrared light. An improved monitoringof the region in front of the vehicle is thus made possible by means ofa display device, such as a picture screen, which is arranged at eyelevel for the vehicle's driver.

Advantageously, the first region comprises a filter coating. Such athin-film filter can be manufactured in a coating process.

In a simple manner, the filter coating forms a semi-circular shell whichsurrounds the lamp bulb around its lower side and allows only infraredlight to enter a lower reflector sector so as to generate an IR highbeam.

In a simple manner, the filter coating envelops the bulb, such that thelamp generates exclusively an IR high beam.

In a simple manner, the filter coating envelops one of two incandescentfilaments of a dual-filament halogen lamp such that in the low-beamposition a low beam formed by light in the visible wavelength range canbe generated by a first incandescent filament, and at the same time ahigh beam formed by light in the infrared wavelength range can begenerated by the second incandescent filament.

Advantageously, the filter coating is provided on a shield. The firstregion of the lamp bulb comprises a shield which is at least partlypermeable to infrared light and at least partly impermeable to visiblelight. If this shield is used in a dual-filament halogen incandescentlamp, and this shield extends below a first filament, then the firstfilament is active in a first, low-beam situation and radiates light inthe visible wavelength range in the form of a low beam, while at thesame time an infrared high beam is generated by the same first filament.In a second, high-beam condition, a second incandescent filament isactive and radiates light in the visible wavelength range as a highbeam.

Advantageously, means are provided on the lamp bulb which safeguard aneutral color impression within a white range. In addition to thefiltered infrared light, a red light in the visible wavelength range hasalso been filtered out undesirably. A purpose-oriented dimensioning andarrangement of a bulb region through which visible light in a blueand/or green wavelength range is issued makes it possible to mix theundesired red light additively with the blue and green light into awhite light. The distance range of this white light may be set for aclose range, and a neutral color impression of the lighting installationcan be achieved.

It is preferred in an embodiment of the invention that means arearranged in the region which is at least permeable to visible light,which means reflect at least partly infrared light into the region whichis at least partly permeable to infrared light and wholly or partlyimpermeable to visible light. The reflected infrared light comprises inparticular the wavelength range of the infrared light which is relevantto the IR night vision apparatus.

An intensification of the infrared light radiated through the firstregion is achieved thereby.

It is furthermore preferred that the light source is constructed as ahalogen lamp or as a gas discharge lamp, since said lamp types complywith the requirements of the automobile industry in particular asregards operational reliability, space occupation, and luminousefficacy.

Advantageously, a lamp bulb has at least a first region which is atleast partly permeable to UV light and infrared light and is at leastpartly impermeable to visible light, and at least a second region whichis wholly or partly permeable at least to visible light. Should thenight vision apparatus fail, i.e. the sensor device or the displaydevice, it is advantageous to supply not only infrared light to thelong-distance region, but at the same time also UV light. It is achievedthereby that traffic signs or UV-reflecting materials, for exampleprovided on persons, can be perceived.

Advantageously, such a filter permeable to UV and IR and blockingvisible light can be provided on a screen or shutter.

Embodiments of the invention will be explained in more detail below withreference to the drawings, in which:

FIG. 1 shows a single-filament halogen lamp with simultaneous low-beamand IR high-beam functions used in a vehicle headlight in a diagrammaticside elevation,

FIG. 2 shows the single-filament halogen lamp inserted into the vehicleheadlight in front elevation,

FIG. 3 shows a single-filament halogen lamp with simultaneous parkinglight and IR high-beam functions in side elevation,

FIG. 4 shows a dual-filament halogen lamp with a first filament for alow-beam function and a second filament for a simultaneous parking lightand IR high-beam function used in a vehicle headlight in a diagrammaticside elevation,

FIG. 5 shows a dual-filament halogen lamp with a first filament forsimultaneous low-beam and IR high-beam functions and a second filamentfor a high-beam function inserted into a vehicle headlight in adiagrammatic side elevation,

FIG. 6 shows a discharge lamp with simultaneous low-beam and IRhigh-beam functions inserted into a headlight in a diagrammatic sideelevation,

FIG. 7 is a diagram for an IR light filter,

FIG. 8 is a diagram for an IR and UV light filter, and

FIG. 9 shows a headlight with a screen in a diagrammatic side elevation.

FIG. 1 shows a headlight 1 with a reflector 2 and a single-filamenthalogen lamp 3 which emits visible light and infrared light. An emissionof light means a generation and radiation of light. An electricallyconducting incandescent filament 5 in the form of a coil is positionedin the interior of a lamp bulb 4. The lamp 3 is arranged in front of thereflector 2, the latter reflecting the visible light and infrared lightradiated by the lamp 3 in a defined manner. A first region 6 of the lampbulb 4 is constructed so as to be at least partly permeable to infraredlight and at least partly impermeable to visible light. This function isachieved by a multiple-layer thin-film filter 7 which is provided on anouter surface 8 of the quartz glass lamp bulb 4 in a conventionalthin-film coating process. The thin-film filter 7 is a filter coating 7in the form of a semi-circular shell provided on the bulb 4 andcomprises fifteen individual layers, in which a layer of a Ta₂O₅material of high refractive index alternates with an SiO₂ material oflower refractive index each time. A second region 9, the uncoated regionof the lamp bulb 4 of quartz glass in this case, is wholly or partlypermeable to the entire wavelength range of the light, i.e. to visiblelight and infrared light. Substantially the entire light emission fromthe lamp bulb 4, in particular in the direction of the reflector 2 ofthe headlight 1, is realized through said two regions 6 and 9 of thelamp bulb 4.

The lamp bulb 4 has a front region 10 which is covered by an anti-dazzlecap 11. Advantageously, the cap is constructed as an infrared filterwhich allows IR light to pass and blocks light in the visible wavelengthrange. The bulb 4 furthermore comprises a pinch region 12 which issubstantially covered by a lamp base 13.

A boundary 16 between the regions 6 and 9 on the outer surface 8 of thelamp bulb 4 runs substantially horizontally and in one plane with anaxis 17 of the filament 5 when the headlight 1 is in the mountedposition. The light issuing from the second region 9 is incidentsubstantially directly on an upper reflector sector 18 of the reflector,which is optimized in a known manner for the low-beam function. Areflector sector 19 facing the thin-film filter 17 reflects the infraredlight in a defined manner, i.e. in particular such that a high-beam orlong-distance range is irradiated, and the infrared light illuminatesthat region of the traffic space in front of the vehicle which is notilluminated by the visible low beam and which extends over a horizontalangular range of approximately ±10°.

Two headlights 1, each capable of generating a low beam and a high beam,form part of a lighting installation of a motor vehicle, whichinstallation in addition comprises a sensor device. A long-distancerange detected by the sensor device can be shown on a display device, sothat objects in a long-distance range are also visible at night. The twovehicle headlights with low-beam functions radiate visible light intothe low-beam region and infrared light into the high-beam region of thetraffic space through separate regions of the lamp bulb, said infraredlight serving to support the night vision function.

A filter 20 reflecting infrared light at least partly into the lowerregion 6 is arranged in the upper region 9 of the bulb 4. The infraredlight for long distance is intensified thereby.

FIG. 2 shows the vehicle headlight 1 with the lamp 3. The lightreflected in the upper reflector sector 18 generates a low beam. Thelight reflected in the lower reflector sector 19 generates a high beam.

FIG. 3 shows a further single-filament halogen lamp 31 which alsoprovides two different lighting functions for a vehicle, i.e. IR lightin the high-beam region for supporting the night vision function andvisible light for serving as a parking light. For this purpose, a lampbulb 32 comprises an infrared filter 34 in a first region 33, whichfilter 34 is at least partly impermeable to visible light andsubstantially permeable to infrared light, and a blue-green filter 36 ina region 35, which filter 36 is permeable in particular to blue andgreen light. Red light in the visible range passes through the infraredfilter 34 in an undesired manner, but said light is additively mixedwith the blue and green light into white light. Said white lightradiates with an intensity such that a parking light can be achieved.

FIG. 4 diagrammatically shows a vehicle headlight 41 for low beam with adual-filament halogen lamp 42 and a reflector 43. The lamp 42 has a lampbulb 44 and a lamp base 45. Two incandescent filaments 46 and 47 and ashield 48 of molybdenum below said first, frontmost incandescentfilament 46 are positioned inside the lamp bulb 44. The molybdenumshield 48 is impermeable to visible light. A first, central region 49 ofthe bulb 44 is at least partly permeable to infrared light and at leastpartly impermeable to visible light. To achieve this, a filter coating50 is provided on the bulb 44 so as to envelop the bulb 44 in a tubularmanner. Undesirably, this region is also permeable to red light in thevisible wavelength range. A second, frontmost region 51 of the bulb 44is free from any coating and permeable to infrared and visible light. Athird, rearmost region 52 is designed so as to be permeable to green andblue light. For this purpose, a filter coating 53 is provided on thebulb 44, enveloping the bulb 44 in a tubular manner. This filter coating-53 is bounded by the filter coating 50 and adjoins the lamp base 45.The frontmost region 51 surrounds the first, front incandescent filament56, while the central and rearmost regions 49 and 52 surround thesecond, rear incandescent filament 47.

In the low-beam operational state, the two incandescent filaments 46 and47 are electrically conducting, i.e. switched on, and radiate light bothin the visible and in the infrared wavelength range. In this low-beamfunctional condition, the first, front incandescent filament 46 radiatesvisible light onto an upper reflector sector 54 and thus produces a lowbeam. The molybdenum shield 48 prevents visible light from reaching alower reflector sector 45 and illuminating a long-distance region. Thesecond, rear incandescent filament 47 generates visible and infraredlight. The filter coating 50 achieves that only infrared light entersthe close range as well as the long-distance range via the two reflectorsectors 54 and 55. At the same time, however, undesirable visible redlight of low intensity passes through the filter coating 50. Theblue-green filter allows blue and green light of low intensity to pass.The blue, green, and red light of low intensity are mixed into a whitelight. The white light can be used as a parking light of such a lowintensity that dazzling of oncoming drivers is made impossible. Shouldthe first, front incandescent filament 46 fail, no low-beam light in thevisible range is generated anymore. The vehicle headlight 41nevertheless provides a parking light, thus forming a demarcation light41. The motor vehicle is still recognizable to oncoming drivers as afour-wheel wide motor vehicle.

FIG. 5 shows a vehicle headlight 61 with a further dual-filament halogenlamp 62. Two incandescent filaments 64 and 65 and a shield 66 below thefirst, front incandescent filament 64 are positioned inside a lamp bulb63 of the dual-filament halogen lamp 62. The shield 66 is at leastpartly permeable to infrared light and at least partly impermeable tovisible light and is formed substantially of quartz glass with a filtercoating 67 of several layers, in which a layer of a Ta₂O₅ material ofhigh refractive index and a layer of SiO₂ material of lower reflectiveindex alternate each time. In the low-beam operational condition, onlythe first, front incandescent filament 64 is switched on and radiateslight. Visible light and infrared light are radiated through an upperbulb region 68 into an upper reflector sector 69 of a reflector 70designed for a low beam. Visible light and infrared light are radiatedinto a lower bulb region 71, where the visible light is filtered out toa high degree by the filter coating 67, so that substantially onlyinfrared light enters a lower reflector sector 72, where an infraredhigh beam is generated. In the high-beam operational condition, the rearincandescent filament 65 only is switched on, radiating infrared andvisible light as a high beam into a long-distance range via the tworeflector sectors 69 and 72.

FIG. 6 shows a headlight 79 with a reflector 80 and a high-pressure gasdischarge lamp 81. The lamp comprises a lamp base 82, an inner quartzglass lamp vessel 83 closed in a vacuumtight manner, and an outer lampbulb 84 of quartz glass. The lamp vessel 83 comprises in mutualopposition a first and a second neck-shaped portion 85 and 86, throughwhich current supply conductors 87 and 88 lead to a pair of electrodes89 and 90. The first neck-shaped portion 85 is fixed in the lamp base82. A support, 91 serves to guide the second current supply conductor 88and supports a casing 92 in which the second neck-shaped portion 86 isfixed. The current supply conductors 87 and 88 are passed through thelamp base 82 and are connected to electrically conductive pins 93 thatextend to the exterior. The lamp vessel 83 comprises an ionizablefilling of xenon, mercury, and metal halides. The bulb 84 has a region94 with a coating 95 which is at least partly permeable to infraredlight and at least partly impermeable to visible light. The coating 95envelops the bulb 84 at least partly, and two strips 96 of the coating95 extend along a bulb axis 97 in a lower half 98 of the bulb 84. Thiscoating 95 prevents light in the visible wavelength range from hitting alower reflector sector 99 and thus generating a high beam in the visiblewavelength range. The coating 95 is a thin-film filter 95 with fifteenindividual layers, alternating between a layer of a Ta₂O₅ material ofhigh refractive index and a layer of an SiO₂ material of lowerrefractive index each time. Undesirably, however, the coating 95 is alsoslightly permeable to red light in the visible wavelength range.Infrared light does pass through this coating 95 and is reflected by thelower-reflector sector 99. A high beam is generated with this infraredlight, irradiating the long distance. The long-distance range can bedisplayed by means of a night vision apparatus. Light in the visiblewavelength range is radiated from a second region 101, serving togenerate a low beam and illuminating a short-distance range with visiblelight.

FIG. 7 is a diagram showing the permeability in percents plotted againstthe wavelength in nanometers for a second coating 95. Visible lightcovers a range of 380 to 780 nm. Adjacent infrared light lies in aregion from 780 to 5000 nm. The permeability of said second coating islow in the visible wavelength range and high in the IR range. Thissecond coating 95, which performs the same function as the one indicatedabove, comprises a total of twelve layers, i.e. starting from a lampbulb surface 96 a first, 38.82 nm thick layer of Fe₂O₃, then a second,99.9 nm thick layer of SiO₂, then a third, 47.06 nm thick layer ofFe₂O₃, a fourth, 102.39 nm thick layer of SiO₂, a fifth, 228.8 nm thicklayer of Fe₂O₃, a sixth, 97.78 nm thick layer of SiO₂, a seventh, 58.95nm thick layer of Fe₂O₃, an eighth, 100.39 nm thick layer of SiO₂, aninth 52.29 nm thick layer of Fe₂O₃, a tenth, 97.97 mm thick layer ofSiO₂, an eleventh, 223.1 nm thick layer of Fe₂O₃, and a twelfth, 194.75nm thick layer of SiO₂. These layers are provided on the surface 100 ofthe bulb 84 in a chemical vapor deposition (CVD) process. For thispurpose, the bulb 84 is positioned in a reactor together with startingmaterials that can be vaporized or are in the gaseous state. Particlesof the starting materials are ionized and deposit themselves on the bulbsurface, reacting on the surface with one another so as to form theTa₂O₅, SiO₂, or Fe₂O₃ layers. An alternative coating method is physicalvapor deposition (PVD).

FIG. 8 is a diagram showing the permeability in percents plotted againstthe wavelength in nanometers for a third coating 95. The filter 95 ispermeable both to UV and to IR light and blocks visible light. UV light,i.e. ultraviolet radiation, lies in a wavelength range below 380 nm.This filter comprises, starting from a lamp bulb surface, a first,118.62 nm thick layer of SiO₂, a second, 84.02 nm thick layer of ZrO₂, athird, 124.00 nm thick layer of SiO₂, a fourth, 80.69 nm thick layer ofZrO₂, a fifth, 121.91 nm thick layer of SiO₂, a sixth, 90.78 nm thicklayer of ZrO₂, a seventh, 129.54 nm thick layer of SiO₂, an eighth,93.00 nm thick layer of ZrO₂, a ninth, 126.78 nm thick layer of SiO₂, atenth, 87.43 nm thick layer of ZrO₂, an eleventh, 106.93 nm thick layerof SiO₂, a twelfth, 73.13 nm thick layer of ZrO₂, a thirteenth, 119.15nm thick layer of SiO₂, a fourteenth, 72.77 nm thick layer of ZrO₂, afifteenth, 87.44 nm thick layer of SiO₂, a sixteenth, 59.97 nm thicklayer of ZrO₂, a seventeenth, 82.66 nm thick layer of SiO₂, aneighteenth, 72.02 nm thick layer of ZrO₂, a nineteenth, 127.92 nm thicklayer of SiO₂, a twentieth, 67.66 nm thick layer of ZrO₂, atwenty-first, 83.18 nm thick layer of SiO₂, a twenty-second, 54.61 nmthick layer of ZrO₂, a twenty-third, 78.57 nm thick layer of SiO₂, atwenty-fourth, 53.80 nm thick layer of ZrO₂, a twenty-fifth, 78.42 nmthick layer of SiO₂, a twenty-sixth, 53.96 nm thick layer of ZrO₂, atwenty-seventh, 75.19 nm thick layer of SiO₂, a twenty-eighth, 56.58 nmthick layer of ZrO₂, a twenty-ninth, 81.74 nm thick layer of SiO₂, athirtieth, 58.64 nm thick layer of ZrO₂, a thirty-first, 122.46 nm thicklayer of SiO₂, a thirty-second, 9.29 nm thick layer of ZrO₂, and athirty-third, 511.25 nm thick layer of SiO₂.

FIG. 9 shows a headlight 110 with a discharge lamp 111, a reflector 112,a screen 113, and a lens 114. The screen 113 is at least partlypermeable at least to infrared light and UV light and at least partlyimpermeable to visible light. For this purpose, the screen of quartzglass has a region 115 with a filter coating 116. An IR and UV high beam117 can be generated thereby via a lower reflector sector 118, while atthe same time a low beam 119 of visible light is made possible.

1. A lamp (3, 31, 42, 62, 81) which radiates visible light and infraredlight, characterized in that a lamp bulb (4, 32, 44, 63, 84) comprisesat least a first region (6, 33, 49, 71, 94) which is at least partlypermeable to infrared light and at least partly impermeable to visiblelight, and at least a second region (9, 35, 51, 68, 101) which is whollyor partly permeable at least to visible light.
 2. A lamp as claimed inclaim 1, characterized in that the first region (6, 33, 49, 71, 94) hasa filter coating (7, 34, 50, 67, 95).
 3. A lamp as claimed in claim 2,characterized in that the filter coating (7) forms a semi-circularshell.
 4. A lamp as claimed in claim 2, characterized in that the filtercoating (34, 50) envelops the bulb (32, 42).
 5. A lamp as claimed inclaim 4, characterized in that the filter coating (50) envelops one (47)of two incandescent filaments (46, 47).
 6. A lamp as claimed in claim 2,characterized in that the filter coating (67) is provided on a shield(66).
 7. A lamp as claimed in claim 1, characterized in that means (36,53) safeguarding a neutral color impression within a white region arearranged on the lamp bulb (32, 44).
 8. A lamp as claimed in claim 1,characterized in that means (20) that reflect infrared light at leastpartly into the first region (6) are arranged in the second region (9).9. A lamp as claimed in claim 1, characterized in that the lamp (3, 31,42, 62, 81) is constructed as a halogen lamp (3, 31, 42, 62) or as a gasdischarge lamp (81).
 10. A lamp (3, 31, 42, 62, 81) radiating visiblelight, UV light, and infrared light, characterized in that a lamp bulb(4, 32, 44, 63, 84) has at least a first region (6, 33, 49, 66) which isat least partly permeable to UV light and infrared light and at leastpartly impermeable to visible light, and at least a second region (9,35, 51, 68, 101) which is wholly or partly permeable at least to visiblelight.
 11. A screen (113) for a headlight (110), characterized in thatthe screen (113) has a region (115) which is at least partly permeableto UV light and infrared light and at least partly impermeable tovisible light.
 12. A headlight with a lamp as claimed in claim 1, orwith a screen as claimed in claim 11.